1. Field of the Invention
The present invention relates to an optical sensor.
2. Description of the Related Art
A general optical sensor adopts an arrangement as disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2004-45284. FIG. 10 is a side sectional view showing the sectional structure of an optical encoder disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2004-45284. As shown in FIG. 10, an IC chip 603 which integrates a photodetector (PD) 610 serving as an optical functional element, e.g., light detection functional element is mounted on the internal bottom of a ceramic package 601 via an Ag paste portion 602.
An electrode land 604 is formed on the IC chip 603. The electrode land 604 ensures electrical connection with the lower portion of a surface emitting laser (SEL) 605 via the Ag paste portion 602.
An Au wiring line 608 ensures electrical connection between an upper electrode 606 on the surface emitting laser (SEL) 605 and an electrode pad 607 formed on the IC chip 603. Also, the Au wiring line 608 ensures electrical connection between an electrode 609 formed inside the ceramic package 601 and the electrode pad 607 on the IC chip 603. This structure electrically connects the IC chip 603 and ceramic package 601. A glass member 612 is bonded to the upper surface of the ceramic package 601 via a resin adhesive 611.
Reference numeral 622 denotes a detection target; and 620 and 621, laser beams.
The above-described structure provides an optical encoder in which the ceramic package 601 incorporates the IC chip 603 which integrates the photodetector 610, the Au wiring line 608 electrically connects the IC chip 603 and ceramic package 601, and the glass member 612 covers the ceramic package 601 to protect connections by the Au wiring lines 608, the IC chip 603, and the like.
The conventional optical sensor described above becomes thick to a certain degree owing to its structure. That is, it is very difficult to reduce the thickness.
More specifically, the following factors thicken the optical sensor.                A space needs to be ensured in the direction of height of the ceramic package 601 in order to incorporate the IC chip 603 in the ceramic package 601 and electrically connect the ceramic package 601 and IC chip 603 via the Au wiring line 608.        A space needs to be ensured in the direction of height of the ceramic package 601 not to apply force to the Au wiring line 608.        The glass member 612 needs to have a predetermined thickness in consideration of strength, and this arrangement thickens the optical sensor.        To electrically connect the ceramic package 601 and IC chip 603 by the Au wiring line 608, even the interval between the ceramic package 601 and the chip 603 needs to be ensured to a certain degree (an area for them is required).        
Hence, the conventional optical sensor becomes larger than the IC chip 603. Such large dimensions hinder the use of the conventional optical sensor at a location where it is difficult to ensure an installation space of predetermined dimensions.